1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * build-id.c
  4 *
  5 * build-id support
  6 *
  7 * Copyright (C) 2009, 2010 Red Hat Inc.
  8 * Copyright (C) 2009, 2010 Arnaldo Carvalho de Melo <acme@redhat.com>
  9 */
 10#include "util.h" // lsdir(), mkdir_p(), rm_rf()
 11#include <dirent.h>
 12#include <errno.h>
 13#include <stdio.h>
 14#include <sys/stat.h>
 15#include <sys/types.h>
 16#include "util/copyfile.h"
 17#include "dso.h"
 18#include "build-id.h"
 19#include "event.h"
 20#include "namespaces.h"
 21#include "map.h"
 22#include "symbol.h"
 23#include "thread.h"
 24#include <linux/kernel.h>
 25#include "debug.h"
 26#include "session.h"
 27#include "tool.h"
 28#include "header.h"
 29#include "vdso.h"
 30#include "path.h"
 31#include "probe-file.h"
 32#include "strlist.h"
 33
 34#include <linux/ctype.h>
 35#include <linux/zalloc.h>
 36
 37static bool no_buildid_cache;
 38
 39int build_id__mark_dso_hit(struct perf_tool *tool __maybe_unused,
 40			   union perf_event *event,
 41			   struct perf_sample *sample,
 42			   struct evsel *evsel __maybe_unused,
 43			   struct machine *machine)
 44{
 45	struct addr_location al;
 46	struct thread *thread = machine__findnew_thread(machine, sample->pid,
 47							sample->tid);
 48
 49	if (thread == NULL) {
 50		pr_err("problem processing %d event, skipping it.\n",
 51			event->header.type);
 52		return -1;
 53	}
 54
 55	if (thread__find_map(thread, sample->cpumode, sample->ip, &al))
 
 
 
 56		al.map->dso->hit = 1;
 57
 58	thread__put(thread);
 59	return 0;
 60}
 61
 62static int perf_event__exit_del_thread(struct perf_tool *tool __maybe_unused,
 63				       union perf_event *event,
 64				       struct perf_sample *sample
 65				       __maybe_unused,
 66				       struct machine *machine)
 67{
 68	struct thread *thread = machine__findnew_thread(machine,
 69							event->fork.pid,
 70							event->fork.tid);
 71
 72	dump_printf("(%d:%d):(%d:%d)\n", event->fork.pid, event->fork.tid,
 73		    event->fork.ppid, event->fork.ptid);
 74
 75	if (thread) {
 76		machine__remove_thread(machine, thread);
 77		thread__put(thread);
 
 78	}
 79
 80	return 0;
 81}
 82
 83struct perf_tool build_id__mark_dso_hit_ops = {
 84	.sample	= build_id__mark_dso_hit,
 85	.mmap	= perf_event__process_mmap,
 86	.mmap2	= perf_event__process_mmap2,
 87	.fork	= perf_event__process_fork,
 88	.exit	= perf_event__exit_del_thread,
 89	.attr		 = perf_event__process_attr,
 90	.build_id	 = perf_event__process_build_id,
 91	.ordered_events	 = true,
 92};
 93
 94int build_id__sprintf(const u8 *build_id, int len, char *bf)
 95{
 96	char *bid = bf;
 97	const u8 *raw = build_id;
 98	int i;
 99
100	for (i = 0; i < len; ++i) {
101		sprintf(bid, "%02x", *raw);
102		++raw;
103		bid += 2;
104	}
105
106	return (bid - bf) + 1;
107}
108
109int sysfs__sprintf_build_id(const char *root_dir, char *sbuild_id)
110{
111	char notes[PATH_MAX];
112	u8 build_id[BUILD_ID_SIZE];
113	int ret;
114
115	if (!root_dir)
116		root_dir = "";
117
118	scnprintf(notes, sizeof(notes), "%s/sys/kernel/notes", root_dir);
119
120	ret = sysfs__read_build_id(notes, build_id, sizeof(build_id));
121	if (ret < 0)
122		return ret;
123
124	return build_id__sprintf(build_id, sizeof(build_id), sbuild_id);
125}
126
127int filename__sprintf_build_id(const char *pathname, char *sbuild_id)
128{
129	u8 build_id[BUILD_ID_SIZE];
130	int ret;
131
132	ret = filename__read_build_id(pathname, build_id, sizeof(build_id));
133	if (ret < 0)
134		return ret;
135	else if (ret != sizeof(build_id))
136		return -EINVAL;
137
138	return build_id__sprintf(build_id, sizeof(build_id), sbuild_id);
139}
140
141/* asnprintf consolidates asprintf and snprintf */
142static int asnprintf(char **strp, size_t size, const char *fmt, ...)
143{
144	va_list ap;
145	int ret;
146
147	if (!strp)
148		return -EINVAL;
149
150	va_start(ap, fmt);
151	if (*strp)
152		ret = vsnprintf(*strp, size, fmt, ap);
153	else
154		ret = vasprintf(strp, fmt, ap);
155	va_end(ap);
156
157	return ret;
158}
159
160char *build_id_cache__kallsyms_path(const char *sbuild_id, char *bf,
161				    size_t size)
162{
163	bool retry_old = true;
164
165	snprintf(bf, size, "%s/%s/%s/kallsyms",
166		 buildid_dir, DSO__NAME_KALLSYMS, sbuild_id);
167retry:
168	if (!access(bf, F_OK))
169		return bf;
170	if (retry_old) {
171		/* Try old style kallsyms cache */
172		snprintf(bf, size, "%s/%s/%s",
173			 buildid_dir, DSO__NAME_KALLSYMS, sbuild_id);
174		retry_old = false;
175		goto retry;
176	}
177
178	return NULL;
179}
180
181char *build_id_cache__linkname(const char *sbuild_id, char *bf, size_t size)
182{
183	char *tmp = bf;
184	int ret = asnprintf(&bf, size, "%s/.build-id/%.2s/%s", buildid_dir,
185			    sbuild_id, sbuild_id + 2);
186	if (ret < 0 || (tmp && size < (unsigned int)ret))
187		return NULL;
188	return bf;
189}
190
191/* The caller is responsible to free the returned buffer. */
192char *build_id_cache__origname(const char *sbuild_id)
193{
194	char *linkname;
195	char buf[PATH_MAX];
196	char *ret = NULL, *p;
197	size_t offs = 5;	/* == strlen("../..") */
198	ssize_t len;
199
200	linkname = build_id_cache__linkname(sbuild_id, NULL, 0);
201	if (!linkname)
202		return NULL;
203
204	len = readlink(linkname, buf, sizeof(buf) - 1);
205	if (len <= 0)
206		goto out;
207	buf[len] = '\0';
208
209	/* The link should be "../..<origpath>/<sbuild_id>" */
210	p = strrchr(buf, '/');	/* Cut off the "/<sbuild_id>" */
211	if (p && (p > buf + offs)) {
212		*p = '\0';
213		if (buf[offs + 1] == '[')
214			offs++;	/*
215				 * This is a DSO name, like [kernel.kallsyms].
216				 * Skip the first '/', since this is not the
217				 * cache of a regular file.
218				 */
219		ret = strdup(buf + offs);	/* Skip "../..[/]" */
220	}
221out:
222	free(linkname);
223	return ret;
224}
225
226/* Check if the given build_id cache is valid on current running system */
227static bool build_id_cache__valid_id(char *sbuild_id)
228{
229	char real_sbuild_id[SBUILD_ID_SIZE] = "";
230	char *pathname;
231	int ret = 0;
232	bool result = false;
233
234	pathname = build_id_cache__origname(sbuild_id);
235	if (!pathname)
236		return false;
237
238	if (!strcmp(pathname, DSO__NAME_KALLSYMS))
239		ret = sysfs__sprintf_build_id("/", real_sbuild_id);
240	else if (pathname[0] == '/')
241		ret = filename__sprintf_build_id(pathname, real_sbuild_id);
242	else
243		ret = -EINVAL;	/* Should we support other special DSO cache? */
244	if (ret >= 0)
245		result = (strcmp(sbuild_id, real_sbuild_id) == 0);
246	free(pathname);
247
248	return result;
249}
250
251static const char *build_id_cache__basename(bool is_kallsyms, bool is_vdso,
252					    bool is_debug)
253{
254	return is_kallsyms ? "kallsyms" : (is_vdso ? "vdso" : (is_debug ?
255	    "debug" : "elf"));
256}
257
258char *dso__build_id_filename(const struct dso *dso, char *bf, size_t size,
259			     bool is_debug)
260{
261	bool is_kallsyms = dso__is_kallsyms((struct dso *)dso);
262	bool is_vdso = dso__is_vdso((struct dso *)dso);
263	char sbuild_id[SBUILD_ID_SIZE];
264	char *linkname;
265	bool alloc = (bf == NULL);
266	int ret;
267
268	if (!dso->has_build_id)
269		return NULL;
270
271	build_id__sprintf(dso->build_id, sizeof(dso->build_id), sbuild_id);
272	linkname = build_id_cache__linkname(sbuild_id, NULL, 0);
273	if (!linkname)
274		return NULL;
275
276	/* Check if old style build_id cache */
277	if (is_regular_file(linkname))
278		ret = asnprintf(&bf, size, "%s", linkname);
279	else
280		ret = asnprintf(&bf, size, "%s/%s", linkname,
281			 build_id_cache__basename(is_kallsyms, is_vdso,
282						  is_debug));
283	if (ret < 0 || (!alloc && size < (unsigned int)ret))
284		bf = NULL;
285	free(linkname);
286
287	return bf;
288}
289
290#define dsos__for_each_with_build_id(pos, head)	\
291	list_for_each_entry(pos, head, node)	\
292		if (!pos->has_build_id)		\
293			continue;		\
294		else
295
296static int write_buildid(const char *name, size_t name_len, u8 *build_id,
297			 pid_t pid, u16 misc, struct feat_fd *fd)
298{
299	int err;
300	struct perf_record_header_build_id b;
301	size_t len;
302
303	len = name_len + 1;
304	len = PERF_ALIGN(len, NAME_ALIGN);
305
306	memset(&b, 0, sizeof(b));
307	memcpy(&b.build_id, build_id, BUILD_ID_SIZE);
308	b.pid = pid;
309	b.header.misc = misc;
310	b.header.size = sizeof(b) + len;
311
312	err = do_write(fd, &b, sizeof(b));
313	if (err < 0)
314		return err;
315
316	return write_padded(fd, name, name_len + 1, len);
317}
318
319static int machine__write_buildid_table(struct machine *machine,
320					struct feat_fd *fd)
321{
322	int err = 0;
323	struct dso *pos;
324	u16 kmisc = PERF_RECORD_MISC_KERNEL,
325	    umisc = PERF_RECORD_MISC_USER;
326
327	if (!machine__is_host(machine)) {
328		kmisc = PERF_RECORD_MISC_GUEST_KERNEL;
329		umisc = PERF_RECORD_MISC_GUEST_USER;
330	}
331
332	dsos__for_each_with_build_id(pos, &machine->dsos.head) {
333		const char *name;
334		size_t name_len;
335		bool in_kernel = false;
336
337		if (!pos->hit && !dso__is_vdso(pos))
338			continue;
339
340		if (dso__is_vdso(pos)) {
341			name = pos->short_name;
342			name_len = pos->short_name_len;
343		} else if (dso__is_kcore(pos)) {
344			name = machine->mmap_name;
345			name_len = strlen(name);
346		} else {
347			name = pos->long_name;
348			name_len = pos->long_name_len;
349		}
350
351		in_kernel = pos->kernel ||
352				is_kernel_module(name,
353					PERF_RECORD_MISC_CPUMODE_UNKNOWN);
354		err = write_buildid(name, name_len, pos->build_id, machine->pid,
355				    in_kernel ? kmisc : umisc, fd);
356		if (err)
357			break;
358	}
359
360	return err;
361}
362
363int perf_session__write_buildid_table(struct perf_session *session,
364				      struct feat_fd *fd)
365{
366	struct rb_node *nd;
367	int err = machine__write_buildid_table(&session->machines.host, fd);
368
369	if (err)
370		return err;
371
372	for (nd = rb_first_cached(&session->machines.guests); nd;
373	     nd = rb_next(nd)) {
374		struct machine *pos = rb_entry(nd, struct machine, rb_node);
375		err = machine__write_buildid_table(pos, fd);
376		if (err)
377			break;
378	}
379	return err;
380}
381
382static int __dsos__hit_all(struct list_head *head)
383{
384	struct dso *pos;
385
386	list_for_each_entry(pos, head, node)
387		pos->hit = true;
388
389	return 0;
390}
391
392static int machine__hit_all_dsos(struct machine *machine)
393{
394	return __dsos__hit_all(&machine->dsos.head);
395}
396
397int dsos__hit_all(struct perf_session *session)
398{
399	struct rb_node *nd;
400	int err;
401
402	err = machine__hit_all_dsos(&session->machines.host);
403	if (err)
404		return err;
405
406	for (nd = rb_first_cached(&session->machines.guests); nd;
407	     nd = rb_next(nd)) {
408		struct machine *pos = rb_entry(nd, struct machine, rb_node);
409
410		err = machine__hit_all_dsos(pos);
411		if (err)
412			return err;
413	}
414
415	return 0;
416}
417
418void disable_buildid_cache(void)
419{
420	no_buildid_cache = true;
421}
422
423static bool lsdir_bid_head_filter(const char *name __maybe_unused,
424				  struct dirent *d)
425{
426	return (strlen(d->d_name) == 2) &&
427		isxdigit(d->d_name[0]) && isxdigit(d->d_name[1]);
428}
429
430static bool lsdir_bid_tail_filter(const char *name __maybe_unused,
431				  struct dirent *d)
432{
433	int i = 0;
434	while (isxdigit(d->d_name[i]) && i < SBUILD_ID_SIZE - 3)
435		i++;
436	return (i == SBUILD_ID_SIZE - 3) && (d->d_name[i] == '\0');
437}
438
439struct strlist *build_id_cache__list_all(bool validonly)
440{
441	struct strlist *toplist, *linklist = NULL, *bidlist;
442	struct str_node *nd, *nd2;
443	char *topdir, *linkdir = NULL;
444	char sbuild_id[SBUILD_ID_SIZE];
445
446	/* for filename__ functions */
447	if (validonly)
448		symbol__init(NULL);
449
450	/* Open the top-level directory */
451	if (asprintf(&topdir, "%s/.build-id/", buildid_dir) < 0)
452		return NULL;
453
454	bidlist = strlist__new(NULL, NULL);
455	if (!bidlist)
456		goto out;
457
458	toplist = lsdir(topdir, lsdir_bid_head_filter);
459	if (!toplist) {
460		pr_debug("Error in lsdir(%s): %d\n", topdir, errno);
461		/* If there is no buildid cache, return an empty list */
462		if (errno == ENOENT)
463			goto out;
464		goto err_out;
465	}
466
467	strlist__for_each_entry(nd, toplist) {
468		if (asprintf(&linkdir, "%s/%s", topdir, nd->s) < 0)
469			goto err_out;
470		/* Open the lower-level directory */
471		linklist = lsdir(linkdir, lsdir_bid_tail_filter);
472		if (!linklist) {
473			pr_debug("Error in lsdir(%s): %d\n", linkdir, errno);
474			goto err_out;
475		}
476		strlist__for_each_entry(nd2, linklist) {
477			if (snprintf(sbuild_id, SBUILD_ID_SIZE, "%s%s",
478				     nd->s, nd2->s) != SBUILD_ID_SIZE - 1)
479				goto err_out;
480			if (validonly && !build_id_cache__valid_id(sbuild_id))
481				continue;
482			if (strlist__add(bidlist, sbuild_id) < 0)
483				goto err_out;
484		}
485		strlist__delete(linklist);
486		zfree(&linkdir);
487	}
488
489out_free:
490	strlist__delete(toplist);
491out:
492	free(topdir);
493
494	return bidlist;
495
496err_out:
497	strlist__delete(linklist);
498	zfree(&linkdir);
499	strlist__delete(bidlist);
500	bidlist = NULL;
501	goto out_free;
502}
503
504static bool str_is_build_id(const char *maybe_sbuild_id, size_t len)
505{
506	size_t i;
507
508	for (i = 0; i < len; i++) {
509		if (!isxdigit(maybe_sbuild_id[i]))
510			return false;
511	}
512	return true;
513}
514
515/* Return the valid complete build-id */
516char *build_id_cache__complement(const char *incomplete_sbuild_id)
517{
518	struct strlist *bidlist;
519	struct str_node *nd, *cand = NULL;
520	char *sbuild_id = NULL;
521	size_t len = strlen(incomplete_sbuild_id);
522
523	if (len >= SBUILD_ID_SIZE ||
524	    !str_is_build_id(incomplete_sbuild_id, len))
525		return NULL;
526
527	bidlist = build_id_cache__list_all(true);
528	if (!bidlist)
529		return NULL;
530
531	strlist__for_each_entry(nd, bidlist) {
532		if (strncmp(nd->s, incomplete_sbuild_id, len) != 0)
533			continue;
534		if (cand) {	/* Error: There are more than 2 candidates. */
535			cand = NULL;
536			break;
537		}
538		cand = nd;
539	}
540	if (cand)
541		sbuild_id = strdup(cand->s);
542	strlist__delete(bidlist);
543
544	return sbuild_id;
545}
546
547char *build_id_cache__cachedir(const char *sbuild_id, const char *name,
548			       struct nsinfo *nsi, bool is_kallsyms,
549			       bool is_vdso)
550{
551	char *realname = (char *)name, *filename;
552	bool slash = is_kallsyms || is_vdso;
553
554	if (!slash) {
555		realname = nsinfo__realpath(name, nsi);
556		if (!realname)
557			return NULL;
558	}
559
560	if (asprintf(&filename, "%s%s%s%s%s", buildid_dir, slash ? "/" : "",
561		     is_vdso ? DSO__NAME_VDSO : realname,
562		     sbuild_id ? "/" : "", sbuild_id ?: "") < 0)
563		filename = NULL;
564
565	if (!slash)
566		free(realname);
567
568	return filename;
569}
570
571int build_id_cache__list_build_ids(const char *pathname, struct nsinfo *nsi,
572				   struct strlist **result)
573{
574	char *dir_name;
575	int ret = 0;
576
577	dir_name = build_id_cache__cachedir(NULL, pathname, nsi, false, false);
578	if (!dir_name)
579		return -ENOMEM;
580
581	*result = lsdir(dir_name, lsdir_no_dot_filter);
582	if (!*result)
583		ret = -errno;
584	free(dir_name);
585
586	return ret;
587}
588
589#if defined(HAVE_LIBELF_SUPPORT) && defined(HAVE_GELF_GETNOTE_SUPPORT)
590static int build_id_cache__add_sdt_cache(const char *sbuild_id,
591					  const char *realname,
592					  struct nsinfo *nsi)
593{
594	struct probe_cache *cache;
595	int ret;
596	struct nscookie nsc;
597
598	cache = probe_cache__new(sbuild_id, nsi);
599	if (!cache)
600		return -1;
601
602	nsinfo__mountns_enter(nsi, &nsc);
603	ret = probe_cache__scan_sdt(cache, realname);
604	nsinfo__mountns_exit(&nsc);
605	if (ret >= 0) {
606		pr_debug4("Found %d SDTs in %s\n", ret, realname);
607		if (probe_cache__commit(cache) < 0)
608			ret = -1;
609	}
610	probe_cache__delete(cache);
611	return ret;
612}
613#else
614#define build_id_cache__add_sdt_cache(sbuild_id, realname, nsi) (0)
615#endif
616
617static char *build_id_cache__find_debug(const char *sbuild_id,
618					struct nsinfo *nsi)
619{
620	char *realname = NULL;
621	char *debugfile;
622	struct nscookie nsc;
623	size_t len = 0;
624
625	debugfile = calloc(1, PATH_MAX);
626	if (!debugfile)
627		goto out;
628
629	len = __symbol__join_symfs(debugfile, PATH_MAX,
630				   "/usr/lib/debug/.build-id/");
631	snprintf(debugfile + len, PATH_MAX - len, "%.2s/%s.debug", sbuild_id,
632		 sbuild_id + 2);
633
634	nsinfo__mountns_enter(nsi, &nsc);
635	realname = realpath(debugfile, NULL);
636	if (realname && access(realname, R_OK))
637		zfree(&realname);
638	nsinfo__mountns_exit(&nsc);
639out:
640	free(debugfile);
641	return realname;
642}
643
644int build_id_cache__add_s(const char *sbuild_id, const char *name,
645			  struct nsinfo *nsi, bool is_kallsyms, bool is_vdso)
646{
647	const size_t size = PATH_MAX;
648	char *realname = NULL, *filename = NULL, *dir_name = NULL,
649	     *linkname = zalloc(size), *tmp;
650	char *debugfile = NULL;
651	int err = -1;
652
653	if (!is_kallsyms) {
654		if (!is_vdso)
655			realname = nsinfo__realpath(name, nsi);
656		else
657			realname = realpath(name, NULL);
658		if (!realname)
659			goto out_free;
660	}
661
662	dir_name = build_id_cache__cachedir(sbuild_id, name, nsi, is_kallsyms,
663					    is_vdso);
664	if (!dir_name)
665		goto out_free;
666
667	/* Remove old style build-id cache */
668	if (is_regular_file(dir_name))
669		if (unlink(dir_name))
670			goto out_free;
671
672	if (mkdir_p(dir_name, 0755))
673		goto out_free;
674
675	/* Save the allocated buildid dirname */
676	if (asprintf(&filename, "%s/%s", dir_name,
677		     build_id_cache__basename(is_kallsyms, is_vdso,
678		     false)) < 0) {
679		filename = NULL;
680		goto out_free;
681	}
682
683	if (access(filename, F_OK)) {
684		if (is_kallsyms) {
685			if (copyfile("/proc/kallsyms", filename))
686				goto out_free;
687		} else if (nsi && nsi->need_setns) {
688			if (copyfile_ns(name, filename, nsi))
689				goto out_free;
690		} else if (link(realname, filename) && errno != EEXIST &&
691				copyfile(name, filename))
692			goto out_free;
693	}
694
695	/* Some binaries are stripped, but have .debug files with their symbol
696	 * table.  Check to see if we can locate one of those, since the elf
697	 * file itself may not be very useful to users of our tools without a
698	 * symtab.
699	 */
700	if (!is_kallsyms && !is_vdso &&
701	    strncmp(".ko", name + strlen(name) - 3, 3)) {
702		debugfile = build_id_cache__find_debug(sbuild_id, nsi);
703		if (debugfile) {
704			zfree(&filename);
705			if (asprintf(&filename, "%s/%s", dir_name,
706			    build_id_cache__basename(false, false, true)) < 0) {
707				filename = NULL;
708				goto out_free;
709			}
710			if (access(filename, F_OK)) {
711				if (nsi && nsi->need_setns) {
712					if (copyfile_ns(debugfile, filename,
713							nsi))
714						goto out_free;
715				} else if (link(debugfile, filename) &&
716						errno != EEXIST &&
717						copyfile(debugfile, filename))
718					goto out_free;
719			}
720		}
721	}
722
723	if (!build_id_cache__linkname(sbuild_id, linkname, size))
724		goto out_free;
725	tmp = strrchr(linkname, '/');
726	*tmp = '\0';
727
728	if (access(linkname, X_OK) && mkdir_p(linkname, 0755))
729		goto out_free;
730
731	*tmp = '/';
732	tmp = dir_name + strlen(buildid_dir) - 5;
733	memcpy(tmp, "../..", 5);
734
735	if (symlink(tmp, linkname) == 0)
736		err = 0;
737
738	/* Update SDT cache : error is just warned */
739	if (realname &&
740	    build_id_cache__add_sdt_cache(sbuild_id, realname, nsi) < 0)
741		pr_debug4("Failed to update/scan SDT cache for %s\n", realname);
742
743out_free:
744	if (!is_kallsyms)
745		free(realname);
746	free(filename);
747	free(debugfile);
748	free(dir_name);
749	free(linkname);
750	return err;
751}
752
753static int build_id_cache__add_b(const u8 *build_id, size_t build_id_size,
754				 const char *name, struct nsinfo *nsi,
755				 bool is_kallsyms, bool is_vdso)
756{
757	char sbuild_id[SBUILD_ID_SIZE];
758
759	build_id__sprintf(build_id, build_id_size, sbuild_id);
760
761	return build_id_cache__add_s(sbuild_id, name, nsi, is_kallsyms,
762				     is_vdso);
763}
764
765bool build_id_cache__cached(const char *sbuild_id)
766{
767	bool ret = false;
768	char *filename = build_id_cache__linkname(sbuild_id, NULL, 0);
769
770	if (filename && !access(filename, F_OK))
771		ret = true;
772	free(filename);
773
774	return ret;
775}
776
777int build_id_cache__remove_s(const char *sbuild_id)
778{
779	const size_t size = PATH_MAX;
780	char *filename = zalloc(size),
781	     *linkname = zalloc(size), *tmp;
782	int err = -1;
783
784	if (filename == NULL || linkname == NULL)
785		goto out_free;
786
787	if (!build_id_cache__linkname(sbuild_id, linkname, size))
788		goto out_free;
789
790	if (access(linkname, F_OK))
791		goto out_free;
792
793	if (readlink(linkname, filename, size - 1) < 0)
794		goto out_free;
795
796	if (unlink(linkname))
797		goto out_free;
798
799	/*
800	 * Since the link is relative, we must make it absolute:
801	 */
802	tmp = strrchr(linkname, '/') + 1;
803	snprintf(tmp, size - (tmp - linkname), "%s", filename);
804
805	if (rm_rf(linkname))
806		goto out_free;
807
808	err = 0;
809out_free:
810	free(filename);
811	free(linkname);
812	return err;
813}
814
815static int dso__cache_build_id(struct dso *dso, struct machine *machine)
816{
817	bool is_kallsyms = dso__is_kallsyms(dso);
818	bool is_vdso = dso__is_vdso(dso);
819	const char *name = dso->long_name;
820
821	if (dso__is_kcore(dso)) {
822		is_kallsyms = true;
823		name = machine->mmap_name;
824	}
825	return build_id_cache__add_b(dso->build_id, sizeof(dso->build_id), name,
826				     dso->nsinfo, is_kallsyms, is_vdso);
827}
828
829static int __dsos__cache_build_ids(struct list_head *head,
830				   struct machine *machine)
831{
832	struct dso *pos;
833	int err = 0;
834
835	dsos__for_each_with_build_id(pos, head)
836		if (dso__cache_build_id(pos, machine))
837			err = -1;
838
839	return err;
840}
841
842static int machine__cache_build_ids(struct machine *machine)
843{
844	return __dsos__cache_build_ids(&machine->dsos.head, machine);
845}
846
847int perf_session__cache_build_ids(struct perf_session *session)
848{
849	struct rb_node *nd;
850	int ret;
851
852	if (no_buildid_cache)
853		return 0;
854
855	if (mkdir(buildid_dir, 0755) != 0 && errno != EEXIST)
856		return -1;
857
858	ret = machine__cache_build_ids(&session->machines.host);
859
860	for (nd = rb_first_cached(&session->machines.guests); nd;
861	     nd = rb_next(nd)) {
862		struct machine *pos = rb_entry(nd, struct machine, rb_node);
863		ret |= machine__cache_build_ids(pos);
864	}
865	return ret ? -1 : 0;
866}
867
868static bool machine__read_build_ids(struct machine *machine, bool with_hits)
869{
870	return __dsos__read_build_ids(&machine->dsos.head, with_hits);
871}
872
873bool perf_session__read_build_ids(struct perf_session *session, bool with_hits)
874{
875	struct rb_node *nd;
876	bool ret = machine__read_build_ids(&session->machines.host, with_hits);
877
878	for (nd = rb_first_cached(&session->machines.guests); nd;
879	     nd = rb_next(nd)) {
880		struct machine *pos = rb_entry(nd, struct machine, rb_node);
881		ret |= machine__read_build_ids(pos, with_hits);
882	}
883
884	return ret;
885}